Despite the efficacy of endovascular thrombectomy (ET), 50% of the patients remain disabled at 3 months. Adjunctive therapies to thrombolysis and ET are needed that provide ?bridging neuroprotection? and improve collaterals. Remote ischemic conditioning (RIC), the simple and safe repetitive inflation-deflation of a blood pressure (BP) cuff on the limbs, improves collateral blood flow in acute stroke. RIC is now being tested in a large phase III randomized, sham-controlled, prehospital acute stroke trial of 1500 subjects in Denmark, the RESIST trial. While nitric oxide synthase 3 (NOS3) was thought restricted to endothelial cells, it is now known that red blood cells (RBCs) express NOS3 and that this erythrocyte NOS3 (eryNOS3) may play a critical role in microvascular blood flow and organ protection during ischemia. We have developed two putative ?rheo- erythocrine? biomarkers: RBC deformability by ektacytometry and eryNOS3 by flow cytometry. Our hypothesis is that RBC deformability and eryNOS3 are ?pharmacodynamic? biomarkers of RIC and will be related to improved outcome in acute stroke. To test this hypothesis we will utilize the clinical trial platform of the RESIST trial for a biomarker substudy. Our specific aims include: Aim 1: Determine if RIC improves rheoerythrocrine biomarkers (RBC deformability, increases activated eryNOS3) and/or increases plasma nitrite compared to sham RIC .Aim 2: Determine if rheo-erythrocrine biomarkers are related to improved short term (24 hr) or long term (90 day mRS) clinical outcome. We expect that RBC deformability and eryNOS3 will be biomarkers of the conditioning response (pharmacodynamic) and predictive of improved clinical outcome in stroke patients.